Experimental results and design guidelines for minichannel condensers using hydrocarbons.

Hydrocarbons (HCs) present favorable thermodynamic and transport properties that make them attractive for use in refrigeration, air conditioning and heat pump systems. Furthermore, HCs display low global warming potential (GWP) and thus they could be an environmentally friendly solution to replace hydrofluorocarbons (HFCs). The major issue related to a wide utilization of HCs in refrigeration industry is their flammability and hence the realization of low charge heat transfer devices is a key factor for their market placement. Despite the favorable characteristics as cost, compatibility with materials and mineral oil, few works in the literature deal with condensation of HCs. In the present paper, new condensation heat transfer coefficients and pressure drop data measured with propylene (R1270) inside a 0.96 mm diameter minichannel are presented. Tests have been performed at 40°C saturation temperature, with mass velocity ranging between 200 and 1000 kg m-2 s-1. In addition, propane (R290) experimental data previously measured inside the same minichannel are reported for comparison. Two correlations for heat transfer and pressured drop available in the literature have been assessed using the present database with the aim to suggest reliable tools for minichannel condenser design. Finally, a comparative analysis between the condensation performance of HCs and two HFCs is reported: the comparison is made with the objective of minimizing the exergy losses, due to the driving temperature difference between saturation and wall and to the frictional pressure drop. An estimation of the condenser refrigerant charge using the different fluids is also performed.

碳氢化合物（Hydrocarbons，HCs）具有优异的热力学和传递特性，使其在制冷、空调及热泵系统中具有应用吸引力。此外，HCs的全球变暖潜能值（Global Warming Potential，GWP）较低，因此可作为替代氢氟烃（Hydrofluorocarbons，HFCs）的环保方案。HCs在制冷行业广泛应用的主要障碍是其易燃性，因此开发低充注量传热设备是推动其市场化的关键因素。尽管HCs具有成本低、与材料及矿物油相容性好等优势，但现有文献中针对其冷凝过程的研究较少。本文报道了在直径为0.96 mm的微通道内，丙烯（propylene，R1270）冷凝传热系数及压降的新实验数据。实验在40℃饱和温度下进行，质量流速范围为200至1000 kg·m⁻²·s⁻¹。此外，还报道了此前在同一微通道内测得的丙烷（propane，R290）实验数据，以供对比分析。利用本文数据库，对现有文献中两种传热及压降关联式进行了评估，旨在为微通道冷凝器设计提供可靠工具。最后，本文对HCs与两种HFCs的冷凝性能进行了对比分析：该对比旨在最小化由饱和温度与壁面温度差及摩擦压降引起的㶲损失。此外，还对使用不同工质时冷凝器的制冷剂充注量进行了估算。